Spinner.cs

    class Program
    {
        static void Main(string[] args)
        {
            var spinner = new Spinner();
            spinner.Start(0, 0);

            Console.WriteLine("Hello World!" + Console.BufferHeight);
            Console.WriteLine("Hello World!" + Console.BufferHeight);
            Console.WriteLine("Hello World!" + Console.BufferHeight);
            while (true)
            {
                spinner.Message = Console.ReadLine();
            }
            //spinner.Stop();

            Console.WriteLine("Spinning should have stopped now.");
            Console.ReadLine();
        }
    }

    public class Spinner
    {
        private readonly string _frames;
        private readonly SpinnerLocation _location;
        private CancellationTokenSource _cancellationTokenSource;

        public string Message { get; set; }

        public Spinner(string frames = @"/-\|", SpinnerLocation? location = null)
        {
            _frames = frames;
            _location = location ?? SpinnerLocation.TopLeft;
        }

        public void Start(int x, int y, string message = null)
        {
            Message = message ?? "";

            _cancellationTokenSource = new CancellationTokenSource();
            var token = _cancellationTokenSource.Token;

            var task = new Task(() =>
            {
                var counter = 0;
                while (!token.IsCancellationRequested)
                {
                    var index = ++counter % _frames.Length;
                    var value = _frames[index].ToString();

                    var initialBackground = Console.BackgroundColor;
                    var initialForeground = Console.ForegroundColor;
                    var initialLeft = Console.CursorLeft;
                    var initialTop = Console.CursorTop;

                    lock (Console.Out)
                    {
                        Console.SetCursorPosition(x, y);
                        Console.BackgroundColor = ConsoleColor.Gray;
                        Console.ForegroundColor = ConsoleColor.Black;

                        value += (Message ?? "").PadLeft(2);

                        Console.Write(value);

                        if (_location == SpinnerLocation.TopLeft)
                        {
                            var width = Console.BufferWidth;
                            var padding = string.Join("", Enumerable.Repeat(' ', width - value.Length));
                            Console.Write(padding);
                        }

                        Console.BackgroundColor = initialBackground;
                        Console.ForegroundColor = initialForeground;
                        Console.SetCursorPosition(initialLeft, initialTop);
                    }

                    Thread.Sleep(1000 / _frames.Length);
                }
            });

            task.Start();
        }

        public void Stop()
        {
            _cancellationTokenSource?.Cancel();
        }

        public enum SpinnerLocation
        {
            TopLeft,
            LineLeft,
            LineRight
        }
    }